The present invention relates to a method of and an apparatus for applying a paint such as a primer, coating material or adhesive.
In order to apply a paint, it is most common either to soak a paint-coating brush with the paint and move the brush while pushing it against the surface of an object to be coated with the paint or to move a nozzle while discharging or spraying the paint therefrom, with the nozzle tip kept away from the surface of the object by a certain distance.
For example, when hinges are to be mounted on the portions G1 and G2 (FIG. 14) of a quarter window glass QG in an automobile manufacturing plant, brushing has been used for applying a black primer BP to the upper surface F1 (FIG. 1), lower surface F2 and end face F3 in the portions G1 and G2.
Consequently, the application of the black primer to each of the portions G1 and G2 has to consist of three steps of motion to which the brush is subjected relative to the quarter window glass QG. Moreover, the quarter window glass QG has to be turned over when the brush has completed the first step of motion, and the attitude of the quarter window glass QG has to be changed when the brush has completed the second step of motion. This requires a great deal of time and labor.
Another trouble is that uniform paint coating within a prescribed range cannot be easily done, that the coat of the paint cannot be made constant in pattern, and that the paint is applied also to areas where it need not be applied. The result is that the paint is wasted, and the workmanship of paint coating lacks consistency. External appearance goes bad because of these troubles, which are caused by the fact that the brush makes a different path every time it is subjected to reciprocating motion.
In order to soak a paint-coating brush with the paint, it is most common (1) to steep the brush in a vessel which contains the paint, (2) to connect a pipe to the root portion of the brush so that the paint may be supplied to the brush through the pipe, or (3) to fixedly mount a paint reservoir on the brush. In the first case, the quantity of the paint with which the brush is soaked cannot be kept constant. Consequently, stringiness or trickling of the paint is liable to occur, and uniform paint coating cannot be done. In the second case, a paint feed pump and the brush must be connected with each other by means of a flexible pipe if the continuous feed of the paint is to be effected. This construction makes it difficult to precisely control the flow of the paint. In the third case, it is not easy to cut off the supply of the paint, and the paint reservoir must be replaced with a new one every time the old one is emptied.
In case where the paint is discharged from a nozzle, it is necessary to precisely control the quantity of the paint discharged per unit time from the nozzle, because the coating thickness is determined thereby. However, it is not easy to precisely control such a quantity.